Open System Services Porting Guide (G06.24+, H06.03+)

Porting or Migrating Sockets Applications
Open System Services Porting Guide—520573-006
11-7
Compiling Native and TNS OSS Programs
•
Marking existing sockets as nonblocking using the fcntl() function
•
Performing reads or writes on any sockets that are ready
•
Handling the errno value EWOULDBLOCK and retrying the input or output
later when necessary
Table 11-2 summarizes the differences between nonblocking (OSS) and nowait
(Guardian) sockets I/O.
Compiling Native and TNS OSS Programs
To compile native OSS applications, you must use the TNS/R or TNS/E native mode
c89 compiler. The following OSS shell command compiles and links the native sockets
program nsock.c:
c89 -o nsock nsock.c -l c -D _XOPEN_SOURCE_EXTENDED = 1
-D _TANDEM_SOURCE
To compile G-series TNS OSS applications, you must use the TNS c89 compiler. TNS
AF_INET sockets applications must be linked with the shared sockets library
libinet.a, which resides in /usr/lib. The following OSS shell command compiles
the TNS sockets program nnsock.c:
/nonnative/usr/c89 -o nnsock nnsock.c -l inet -l c
-D _XOPEN_SOURCE_EXTENDED = 1 -D _TANDEM_SOURCE
See the C/C++ Programmer’s Guide and the nld Manual, the ld Manual, or the eld
Manual for more information on compiling and linking native C and C++ programs.
Table 11-2. Major Differences Between OSS and Guardian Sockets Input/Output
OSS Nonblocking I/O Guardian Nowait I/O
A socket is created with socket() and
fcntl(fd, F_SETFL,O_NONBLOCK)
makes the socket nonblocking.
A socket is created as waited with
socket()
or as a nowait socket with socket_nw().
When a socket I/O call is made, control is
returned immediately to the application.
Either the operation is performed or the
error
EWOULDBLOCK is returned.
When a socket I/O call is made, control is
returned immediately to the application. The
operation is performed concurrently with the
application execution. The status of the I/O
completion must be checked with a Guardian
procedure call.
A socket operation requires a single buffer.
For example, four recv() calls require one
buffer.
Every socket operation requires a separate
preallocated buffer. For example, four recv()
calls require four buffers.
The
select() function waits for
specified file descriptors for the next
opportunity to issue a nonblocking I/O call.
AWAITIOX operates on file numbers rather
than file descriptors. FILE_COMPLETE_ allows
waiting for completion on file numbers and on
the readiness of file descriptors;
FILE_COMPLETE_ therefore acts like a
combination of AWAITIOX and select().